I borrowed a copy of Full Throttle last week, and I've just played to the part where you have to figure out how to cross the busted bridge. I can tip over the truck and read the sign at the gorge, but when I try to leave the area I get a message saying 'Set MineRoad - you can now jump the broken bridge'. Stuff appears in my inventory that weren't there before, and when I go back to the gorge the ramp is already in place. So I've missed the entire puzzle about getting the things you need to get across. What do I have to do to turn off this option so I can play through this part of the game?